A valve timing control device is known which controls valve opening and closing timings in response to the drive condition of the internal combustion engine. For example, a control device disclosed in Japanese Patent Publication No. 3365199 includes a timing pulley having a partition wall defining plural hydraulic chambers in the inner periphery thereof, a rotation member having a vane dividing the hydraulic chamber into a hydraulic operating chamber for rotating a cam shaft toward an advance angle direction relative to the timing pulley and a hydraulic operating chamber for rotating the cam shaft toward a retard angle direction relative to the timing pulley, a hydraulic passage for supplying or discharging an operating oil to each hydraulic operating chamber in communication therewith, an oil pressure adjusting means for controlling the supply and discharge of the operating oil to and from each passage and a phase maintaining mechanism for maintaining the phase difference between the timing pulley and the rotation member.
Further, as other related art, a Japanese Patent Publication 2000-282821 A discloses a valve timing control device which includes a groove shaped oil film maintaining means between an axial end surface of mutually sliding rotation members and an end surface of a plate member which supports the rotation member to solve the problem of insufficient oil film on the sliding surface.
Further, as other related art, a Japanese Patent Publication 2002-276312 A discloses a valve timing control device which includes a torsion spring for biasing the rotation member in an advance angle direction to both decrease the volume of the retard angle chamber and to increase the volume of the advance angle chamber by assisting the operation of the vanes.
The first related art, Japanese Patent Publication No. 3365199 discloses an oil supply structure for supplying a very small amount of operating oil exuded from the vane operating oil filled hydraulic chamber onto the sliding surface of the sliding member. This structure, however, is not an active supply system for supplying positively the operating oil onto the sliding surface. This structure may lead to oil film shortage on the sliding surface and, further, friction between the sliding surfaces may increase if foreign matter or abrasion powder penetrates the sliding surfaces. Such impediments may adversely affect the operational responsiveness of the vanes (vane operation delays), and abrasion of the friction members may be accelerated.
According to the valve timing control device disclosed in the second related art, Japanese Patent Publication 2000-282821 A, the operating oil is liquid-tightly sealed in the groove by the oil film maintaining means, and gradually sludge, or foreign matter, is accumulated at the oil film maintaining means, thus eventually resulting in a deterioration in the level of lubrication performance.
According to the valve timing control device disclosed in the third related art, Japanese Patent Publication 2002-276312 A, the operational responsiveness of the vane can be enhanced when the vane is advanced against the reaction force from the cam mechanism. This is because the torsion spring assists the vane operation in an advance direction. However, the contact resistance between the torsion spring and the rotation member is too large, and leads to unstable vane operation, and the switching of vanes may not be smoothly performed. Further, the sliding member is worn out earlier due to the contact resistance between the torsion spring and the rotation member.
Accordingly, this invention pertains to a stable supply of operating oil, while avoiding shortages of oil film on the sliding surface. Further, the invention pertains to improvements in supply of operating oil to sliding surfaces at vanes, advanced or retarded. A need accordingly exists for a valve timing control device with an improved performance in which operating oil can be stably supplied to sliding members.